1. Field of the Invention
The present invention relates to a pillow type packaging apparatus. More particularly, the present invention relates to a pillow type packaging apparatus capable of packaging an article efficiently with agreeable appearance without fail, typically in a manner of a gusseted bag.
2. Description Related to the Prior Art
A pillow type packaging apparatus operates to wrap an article into a bag or packaging by use of continuous sheet material, to obtain a package. In the packaging operation, the outer form of the article is also obtained by way of an auxiliary guide member for the tube forming to keep a tubular shape of the packaging bag. If a shape of a tube forming guide unit as viewed in cross section is different from that of the article as viewed in cross section, it is extremely difficult to obtain the package with agreeable appearance. Also it is extremely difficult without the article to form the packaging bag being empty in a desired size. When supply of the article is stopped, for example, for changing the size and shape of the packaging bag, it is required to supply a dummy article to stabilize the tube forming operation. Even if there is an unusable or unacceptable portion in the continuous sheet material such as a connected portion, it is difficult to remove the unusable part of the continuous sheet material from the apparatus without the article. It is necessary to wrap the article, remove the article from the unusable packaging bag, and then wrap the article again.
JP-Y 38-7673 and JP-Y 55-23922 disclose a use of an inner guide frame, which is disposed inside the tube forming guide unit, for guiding the continuous sheet material inside its tubular portion.
When the continuous sheet material used for the packaging operation is highly rigid, for example 100 microns or more thick, a problem arises by shortening a tube forming distance to deform the continuous sheet material in an abrupt manner. Fine wrinkles (called "darts") occur on the continuous sheet material, to increase resistance to tube forming remarkably. JP-A 63-272607 (corresponding to U.S. Pat. No. 4,761,937) suggests solution of this problem. The tube forming resistance is reduced by disposing a roller or arcuate member in a bending position in the tube forming guide unit for bending the continuous sheet material.
This idea has a shortcoming in that a path length of the continuous sheet material in a width direction between a position before the tube forming guide unit and a position after it is not regular. The term "path length" herein is used to represent a length of a locus of the continuous sheet material being sent through the tube forming guide unit. Thus tension of the continuous sheet material in the width direction is irregular. Possibility of occurrence of zigzag movement of the continuous sheet material is high. The continuous sheet material, typically with low resiliency, does not run smoothly even by use of the roller or arcuate member. Wrinkles may occur more frequently. If the tube forming guide unit has a curved portion, it is difficult to maintain similarity of a shape of the guide unit after a change in the size to its shape before the change.
In general, a tube forming distance is determined sufficiently in the apparatus for the tube forming of the continuous sheet material with low resiliency. This is because the difference along the path length of the continuous sheet material in the width of the continuous sheet material between upstream and downstream positions from the tube forming guide unit should be absorbed, even though the continuous sheet material has a low tendency of extension and compression.
In the pillow type packaging apparatus, the article should be supplied to the tube forming guide unit while positioned at a regular interval, article from article, for the purpose of preventing the article from colliding with a bottom sealer. There are suggestions for this positioning, which have been implemented in practical use. JP-B 58-44525 (corresponding to JP-A 54-138792) discloses a mechanical construction for positioning each article by use of a pusher. JP-B 7-67922 (corresponding to JP-A 4-44912) discloses an electric construction according to which a sensor is disposed directly before the tube forming guide unit, and a supply conveyor is s tart ed in response to a signal from the sensor.
The continuous sheet material after the tube forming for the tubular shape is subjected to a station of gusset forming shortly before the bottom sealer. In the gusset forming, lateral faces of the continuous sheet material are folded inward. The continuous sheet material is collapsed and flattened in a vertical direction, to discharge air from between two consecutive articles. JP-B 7-108689 (corresponding to JP-A 2-282004) discloses gusset forming in which the bottom sealer is used by way of a tube forming guide unit. The bottom sealer is moved, for example, according to a technique of the box motion.
There is a problem in that a conveyor, which conveys the article being packaged, is likely to interfere with the bottom sealer. JP-B 7-64326 (corresponding to JP-A 2-282005) suggests a solution, according to which the conveyor is extended and shortened. A conveyor belt unit consists of upstream and downstream conveyor sections, in which a common single belt is connected in a roll form. The belt roll is horizontally moved to change an interval between upstream and downstream conveyor sections. An interval between the conveyor sections is increased for allowing heaters above and below a conveying path to operate for the center sealing, and changed as zero (0) in a closed state with the heaters retracted vertically from the conveying path.
JP-Y 38-7673 and JP-Y 55-23922 disclose the inner guide frame, which, however, is changeable in the size only in the width direction of the packaging bag. No suggestion exists for an inner guide frame changeable in the size in a vertical direction of the packaging bag. In changing the size of the tube forming guide unit, the tube forming state should be adjusted while the continuous sheet material is manually supplied by an operator. The pillow type packaging apparatus known so far in the art is comparatively unadvantageous in comparison with other types of packaging apparatus, because of low suitability to changing the size of the continuous sheet material.
It is important that the tube forming guide unit should have a shape with a constant path length between upstream and downstream positions from the tube forming guide unit in any position of the continuous sheet material in its width direction, to prevent looseness in forming the continuous sheet material into the tubular shape. JP-B 60-55364 (corresponding to JP-A 58-64908) discloses an example of a shape of the tube forming guide unit. However the tube forming guide unit has a continuous surface. If the size of the packaging bag is required to change, the tube forming guide unit must be entirely exchanged or deformed.
In the known apparatuses, the inner guide frame is only inserted in an opening of the tube forming guide unit. There occurs looseness in the packaging bag in association with a gap between the tube forming guide unit and the inner guide frame. It is likely that tightness in the bottom sealed portion becomes low due to wrinkles caused in the gusset forming. It is likely that there occurs failure in the gusset forming such as deviations between a folded line of gussets and any of four lateral edges of the packaging bag.
The above-mentioned apparatus with the tube forming distance being great has an inevitably great size. If an accident occurs in the tube forming guide unit, it is extremely difficult to pass the continuous sheet material in the packaging apparatus initially for next operation. It is also necessary to remove a considerable number of inserted test articles from the line, and insert dummy articles to stabilize the forming of the packaging bag before safely starting the packaging operation.
JP-B 58-44525 (corresponding to JP-A 54-138792) and JP-B 7-67922 (corresponding to JP-A 4-44912) suggest the positioning method of an interval between articles with prevention of collision between the article and the bottom sealer. However it is difficult to check the article in the tube forming guide unit for exactness in the regular interval in the arrangement. If an operator manually adjusts the apparatus for eliminating difficulties in the tube forming guide unit, collision may occur again i n the article and the bottom sealer resulting in drawbacks of the known method. The interval between the articles changes depending upon a height of the article. The packaging apparatus suitable for plural sizes has a difficulty in positioning the article at a suitable interval again upon restarting of the apparatus after the operator's adjustment.
JP-B 7-108689 (corresponding to JP-A 2-282004) has a shortcoming in that the packaging bag is the more difficult to produce according to a height of the packaging bag. More continuous sheet material than required is used. To effect the above-mentioned box motion, a relevant mechanism must have a complicated structure due to synchronization between conveyance of the article and movement of the bottom sealer.
A gusseted portion should be formed by bending four faces of the continuous sheet material of the tubular shape with bender members swingable about their respective axes. The respective axes of the bender members are not positioned along sides of an end face of the article according to any of the known constructions, and do not form a gusseted portion with agreeable appearance. Also, known bender members are likely to damage the continuous sheet material.
If a considerable amount of air remains in the packaging bag, the continuous sheet material must be used to a greater extent. It is difficult to stabilize a packaging operation. To reduce this surplus amount of the continuous sheet material, there is a suggestion for a suction nozzle to be inserted into the tube forming guide unit to discharge the remaining air from the article. However it is difficult to adapt this suggestion to packaging an article not quadrangular as viewed in cross section.
JP-B 7-64326 (corresponding to JP-A 2-282005) discloses a use of a conveyor belt for conveying the article and an extensible structure for the conveyor belt. However this idea cannot be applied to a use of an accumulate conveyor. It is general to use a method of preventing interference with the bottom sealer by shifting the conveyor. However the conveyor of the shiftable type requires spaces in forward and reverse directions for shifting stroke. It is impossible at the same time to effect reception and delivery of the articles, so that cycle time becomes excessively-long, and inconsistent to heightening efficiency.
In the pillow type packaging apparatus where the packaging bag is supplied and the article is inserted into the packaging bag before a bag mouth of the packaging bag is closed, the closing operation is influenced by the article, the remaining air or the like. It is difficult to close the bag mouth of the packaging bag in the same state as before opening the bag mouth without difference. Typically with the gusseted bag, a process is required for folding the gusseted portion inwards in closing the packaging bag.
There are suggestions to solve this problem. JP-B 7-41895 (corresponding to JP-A 5-330518) discloses a use of force of suction for retaining the packaging bag. JP-B 52-229672 (corresponding to U.S. Pat. No. 3,859,062) discloses an operation of squeezing the bag mouth with a chuck. However the former has a shortcoming due to small force of retention with the suction. The latter must have a complicated mechanical structure for the chuck. Another shortcoming is a relatively great number of packaging steps because of insertion of the chuck into the packaging bag.
JP-B 61-44725 (corresponding to JP-A 55-134003) discloses a method in which the chuck squeezes the bag mouth, and rotating and moves toward the article for creating a folded end. The rotation and movement of the chuck are synchronized by engagement of a rack and a pinion.
If the chuck of the plate shape is used for folding the bag mouth, the chuck must be moved along a path of a sine curve when the chuck is rotated at a constant speed. It is impossible to keep tension applied to the continuous sheet material during the folding operation of the bag mouth. The bag mouth cannot be folded tightly typically when the article is fragile with small rigidity, or has an edge liable to be damaged.
If excessive tension is applied to the continuous sheet material for the purpose of tight folding, air is likely to enter the bag mouth to expand the packaging bag after the end folding, so that a difficulty may occur in a succeeding process. It is further likely that the chuck is not removed from the bag mouth after folding the bag mouth.
To solve this problem, JP-A 2-19223 suggests a construction in which a rotational shaft of the chuck is so eccentric that the rotational shaft lies on a folding line of the continuous sheet material, and the rotational shaft is moved each time that the chuck makes half a rotation. However it is extremely difficult to rotate and move the chuck at the same time. Also it requires a complicated mechanism.
JP-B 55-13976 (corresponding to JP-A 49-3937) discloses a method of attaching a tape to a package. A tape attacher roller is pressed to the article by moving along a line lying on an end face of the article, so as to attach the tape in the L-shape for enclosing the bag mouth firmly. This is an acceptable method if the article in the package is sufficiently rigid, for example a corrugated fiberboard box. However edges of the article are likely to be damaged by pressure of the tape attacher roller if the article in the package is fragile, and with the continuous sheet material being fragile.
In the apparatus, a front end of the tape is captured by the chuck. The tape is supplied by a regular length, is cut and then is attached to the article. It is necessary to retain a rear end of the tape by means of the suction on the side of a roll of the unused tape. A target portion to be captured by the chuck should be previously free. The tape with small rigidity in a general manner, however, has instability in the position of the front end after the cutting operation. Failure is likely to occur in capturing of the chuck.
JP-A 3-176344 suggests a method of retaining the front end of the tape by use of the suction. However it is extremely difficult to determine the sucking force greater than adhesive force of the tape. The tape cannot be run stably.